For the purpose of three-dimensionally representing an object, three-dimensional Computer Aided Design (3D CAD) is used. According to the Japanese Industrial Standards (JIS) B3401, CAD is defined as “a design by generating inside of a computer a model formed of shape and other attribute data of a product for analysis and processing”.
In the conventional 3D CAD, to display only the outer shape of an object, data representing the shape of the object with inner components deleted is generated by a user and is then used by an apparatus to display the outer shape of the object. Moreover, the data is generated by the user selecting components unnecessary to display only the outer shape of the object and by the apparatus deleting data regarding the components selected by the user. One known technique is a unification technique of unifying a plurality of components into one for display, thereby simplifying the object.
Examples of the conventional techniques are disclosed in Japanese Laid-open Patent Publication No. 10-143682 (pp. 1-3, FIG. 1) and Japanese Laid-open Patent Publication No. 05-250445 (pp. 1-4, FIG. 1).
Meanwhile, in the conventional techniques, it is impossible to display only the outer shape without requiring any additional data. That is, the apparatus cannot display only the outer shape unless data representing only the outer shape is generated by the user. In the unification technique explained above, the shape of the object is changed, and an outer-shape model cannot be generated.